Polymeric materials have been utilized in the past as electrical insulating materials for electrical cables. In services or products requiring long-term performance of an electrical cable, such polymeric materials, in addition to having suitable dielectric properties, must be durable. For example, polymeric insulation utilized in building wire, electrical motor or machinery power wires, or underground power transmitting cables, must be durable for safety and economic necessities and practicalities.
The most common polymeric insulators are made from either polyethylene homopolymers or ethylene-propylene elastomers, otherwise known as ethylene-propylene-rubber (EPR) and/or ethylene-propylene-diene ter-polymer (EPDM). Lead, such as lead oxide, has been used as water tree inhibitor and ion scavenger in filed EPR or EPDM insulation; however, lead is toxic.
Coated cables which simultaneously have fire-resistance properties and moisture-resistance properties are also desirable. Typical fire retardants are used in the insulation. Halogenated additives (compounds based on fluorine, chlorine or bromine) or halogen containing polymers (e.g. polyvinyl chloride) are capable of giving fire-resistant properties to the polymer which forms the insulation, but has the drawback that the decomposition products of halogenated compounds are corrosive and harmful As a result, the use of halogens, especially for uses in closed locations, is not recommended.
Alternatively, or in combination with the halogens, a flame retardant additive, such as antimony oxides, can be added to an appropriate insulation polymer.
Therefore, there remains a need for an environmentally friendly moisture resistant and fire resistant cable insulation that is lead free, halogen free, and antimony free.